Stretched polymer fibers have significantly higher mechanical properties than non-stretched fibers. For example, stretched polymer fibers may have a significantly higher elastic modulus and significantly higher strength than non-stretched polymer fibers formed of the same material. Conventional methods of forming stretched fibers including drawing fibers during an in-line fiber drawing process while maintaining the fibers at an elevated temperature. The fibers may be maintained at an elevated temperature by passing the fibers through an oven during an annealing process.
The fibers must be held at the elevated temperature for a sufficiently long residence time to avoid partially annealing the fibers. Partially annealed fibers present the risk of fiber snap-back or shrinkage during thermal cycling such as may occur due to temperature changes in the operating environment of an article containing the fibers. Snap-back of the fibers may result in a reduction in the mechanical properties of the fibers and the composite structure. Unfortunately, the relatively long residence time during which the fibers must be held at an elevated temperature limits the throughput or rate at which stretched fibers may be produced. Increasing the fiber drawing speed to increase fiber throughput requires a longer oven to maintain the same residence time. Unfortunately, increasing the length of an oven is cost-prohibitive.
As can be seen, there exists a need in the art for a system and method for a method of producing stretched fibers for composite articles in a timely and cost-effective manner.